A Japanese whaling fleet has left port under tight security at the start of Japan’s first whale hunt since a UN court last month ordered Tokyo to stop killing whales in the Antarctic Ocean.

Four ships left the southeastern Japanese fishing town of Ayukawa on April 26 as part of the country’s annual "coastal whaling program," which was not part of last month's ruling by the International Court of Justice (ICJ).

The freshly launched hunt holds symbolic importance as critics call for Japan to end the killing of whales.

The UN court in March ruled that Japan's Southern Ocean expedition was an illegal commercial activity masquerading as scientific research.

In response, Tokyo canceled the Antarctic expedition for 2014-15, saying it would reconfigure the mission to make it more scientific.

Japan has continued hunting whales despite a 1986 global moratorium on the practice, exploiting a loophole in the rule that allows nations to conduct lethal research.

Tokyo says its research is aimed at proving the global whale population is sufficient to allow the resumption of commercial whaling.